The present invention relates to a positive photoresist composition for use in the ultramicrolithography process and other photofabrication processes, such as production of VLSI (Very Large Scale Integration) and high-capacitance micro-chip. More specifically, the present invention relates to a positive photoresist composition capable of forming a highly precise pattern using light in the far ultraviolet region including an excimer laser ray, particularly, in the region of 250 nm or less.
In recent years, the integration degree of integrated circuits is more and more elevated and in the production of a semiconductor substrate such as VLSI, an ultrafine pattern consisting of lines having a width of half micron or less must be worked. To meet this requirement, the wavelength used in the exposure apparatus for photo-lithography increasingly becomes shorter and at the present time, studies are being made on the use of an excimer laser ray (e.g., XeCl, KrF, ArF) having a short wavelength among far ultraviolet rays.
In the formation of a pattern for lithography using this wavelength region, a chemical amplification-system resist is used.
The chemical amplification-system resist in general can be roughly classified into three groups, that is, commonly called 2-component system, 2.5-component system and 3-component system. The 2-component system uses a combination of a compound capable of generating an acid by the photochemical decomposition (hereinafter referred to as a xe2x80x9cphoto-acid generatorxe2x80x9d) and a binder resin. This binder resin is a resin having within the molecule thereof a group capable of decomposing under the action of an acid and thereby increasing solubility of the resin in an alkali developer (also called acid-decomposable group). The 2.5-component system contains a low-molecular weight compound having an acid-decomposable group in addition to the 2-component system. The 3-component system contains a photo-acid generator, an alkali-soluble resin and the above-described low-molecular weight compound.
The chemical amplification-system resist is suitable as a photoresist for use under irradiation with an ultraviolet ray or a far ultraviolet ray but still in need of coping with the characteristics required on use. For example, a resist composition using a polymer obtained by introducing an acetal or ketal protective group into a hydroxystyrene-base polymer which exhibits small light absorption particularly for light at 248 nm of a KrF excimer laser has been proposed in JP-A-2-141636 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), JP-A-2-19847, JP-A-4-219757, JP-A-5-281745 and the like. In addition, a similar composition using a t-butoxycarbonyloxy or p-tetrahydropyranyloxy group as the acid-decomposable group has been proposed in JP-A-2-209977, JP-A-3-206458 and JP-A-2-19847.
These compositions are suitable for the case of using light at 248 nm of the KrF excimer laser, however, when an ArF excimer laser is used as the light source, the substantial absorbance is still excessively large and therefore, the sensitivity is low. Accompanying this, other problems arise, such as deterioration in the resolution, the focus allowance or the pattern profile. Thus, improvements are necessary in many points.
As a photoresist composition for use with an ArF light source, a resin in which an alicyclic hydrocarbon site is introduced so as to impart dry etching resistance has been proposed. Examples of this resin include resins obtained by copolymerizing a monomer having a carboxylic acid site such as acrylic acid or methacrylic acid or a monomer having a hydroxyl group or a cyano group within the molecule, with a monomer having an alicyclic hydrocarbon group.
Other than the above-described method of introducing an alicyclic hydrocarbon site into the side chain of an acrylate-base monomer, a method of using an alicyclic hydrocarbon site in the polymer main chain to impart dry etching resistance is also being studied.
Furthermore, JP-A-9-73173, JP-A-9-90637 and JP-A-10-161313 describe a resist material using an acid-sensitive compound containing an alkali-soluble group protected by a structure containing an alicyclic group, and a structural unit for allowing the alkali-soluble group to be released under the action of an acid and render the compound alkali-soluble.
In addition, a resin obtained by introducing a hydrophilic 5- or 6-membered ring lactone group into the above-described resin having an alicyclic group so as to improve the affinity for an alkali developer or the adhesion to a substrate is described in JP-A-9-90637, JP-A-10-207069, JP-A-10-274852 and JP-A-10-239846.
However, these techniques are insufficient in many points such as improvement for higher sensitivity and higher resolution or improvement of the adhesive property to a substrate, and they are still in need of improvements.
Also, in recent years, to cope with the requirement for semiconductor chips in a finer size, the design pattern for the fine semiconductor has reached to a region as fine as 0.13 to 0.35 xcexcm. The above-described compositions have, however, a problem in that the resolution of the pattern is inhibited due to the factors such as edge roughness of the line pattern or the like. The term xe2x80x9cedge roughnessxe2x80x9d as used herein means the fact that due to the properties of the resist, the edges at the top and bottom of a resist line pattern irregularly fluctuate in the direction perpendicular to the line direction and unevenness is observed on the edges when viewed from right above.
With respect to the photoresist composition for use with an ArF light source, a resin in which an alicyclic hydrocarbon site is introduced so as to impart dry etching resistance has been proposed. However, the system disadvantageously becomes extremely hydrophobic due to the alicyclic hydrocarbon site introduced, as a result, the resist may not be developed with an aqueous tetramethylammonium hydroxide (hereinafter referred to as xe2x80x9cTMAHxe2x80x9d) solution which has been heretofore widely used as a developer for resists or there may arise a phenomenon such that the resist falls off from the substrate during the development.
With an attempt to overcome this hydrophobitization of the resist, an organic solvent such as isopropyl alcohol is mixed in the developer. This gains a certain result but still suffers from problems such as swelling of the resist film or the cumbersome process. From the standpoint of improving the resist, a large number of techniques have been proposed, for example, the hydrophobitization ascribable to various alicyclic hydrocarbon sites is compensated for by introducing a hydrophilic group.
JP-A-10-10739 discloses an energy-sensitive resist material containing a polymer obtained by polymerizing a monomer having an alicyclic structure such as norbornene ring in the main chain, a maleic acid anhydride and a monomer having a carboxyl group. JP-A-10-111569 discloses a radiation-sensitive resin composition containing a resin having an alicyclic skeleton in the main chain and a radiation-sensitive acid generator. JP-A-11-109632 discloses use of a resin containing a polar group-containing alicyclic functional group and an acid-decomposable group, for a radiation-sensitive material.
The resin having an acid-decomposable group, which is used in the photoresist for far ultraviolet exposure, generally contains an aliphatic cyclic hydrocarbon group within the molecule at the same time. Therefore, the resin becomes hydrophobic and there arise problems attributable to it. For overcoming the problems, various techniques have been aggressively investigated as described above, however, these techniques are insufficient in many points (particularly in the developability) and improvements are demanded.
That is, the technique of using a light source of emitting a far ultraviolet ray of short wavelength, for example, an ArF excimer laser (193 nm) is still in need of improvements in view of the developability. To speak specifically, the problem is the development failure, scum (development residue) or edge roughness. Furthermore, the defocus latitude depended on line pitch is also in need of improvements. Devices in recent years have a tendency to contain various patterns, therefore, the resist is required to have various capabilities. One of these capabilities is the defocus latitude on line pitch. More specifically, a device has a portion where lines are crowded, a pattern where the space is broad as compared with lines, and isolated lines. Therefore, it is important to resolve various lines with high reproducibility. However, reproduction of various lines cannot be easily attained because of optical factors and the resist is not yet succeeded in undertaking the part of solving this problem at present. In particular, the above-described resist system containing an alicyclic group conspicuously varies in the reproducibility between the isolated pattern and the crowded pattern, and improvements are being demanded.
For the coating solvent of naphthoquinone-diazide/novolak resin-base positive photoresists, glycol ethers, glycol ether esters such as 2-methoxyethanol and 2-ethoxyethanol, acetates thereof such as ethylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate have been heretofore commonly used.
However, these solvents have problems in the toxicity, the coatability, the storage stability of the solution, the resist performance and the like, and improvements thereof are demanded.
The coatability, the storage stability of the solution and the resist performance are, as well known, attributes to the constituent components such as binder polymer and photo-acid generator and at the same time greatly fluctuated by the solvent. As such, the resist solvent is demanded to satisfy all requirements with respect to the coatability, the storage stability of the solution, the safety, the resist performance and the development failure, however, the fact is that such a solvent has been not known for the chemical amplification resist using a polymer having an alicyclic hydrocarbon skeleton.
Thus, conventional photoresist compositions in known arts cannot respond to the recently required performance in the sensitivity, the resolution or the adhesion to a substrate. Moreover, scumming or edge roughness is generated or a stable pattern cannot be obtained. Under these circumstances, more improvements are being demanded.
Accordingly, an object of the present invention is to provide a chemical amplification-type positive photoresist composition favored with high sensitivity, high resolution and good adhesion to a substrate and improved in the edge roughness of a pattern.
Another object of the present invention is to solve the problems encountered in the techniques for improving the capabilities inherent in the above-described micro-photofabrication using far ultraviolet rays, particularly ArF excimer laser rays, more specifically, to provide a positive photoresist composition excellent in the sensitivity, resolution, dry etching resistance and adhesion to a substrate and freed from the problems occurring at the development, namely, generation of development failure, scumming or edge roughness.
Still another object of the present invention is to provide a positive photoresist composition for far ultraviolet exposure, favored with an excellent defocus latitude depended on line pitch.
Still another object of the present invention is to provide a positive photoresist composition for far ultraviolet exposure, favored with an excellent defocus latitude depended on line pitch and improved in the edge roughness of a pattern.
As a result of extensive studies on the constituent materials of a resist composition in the positive chemical amplification system, the present inventors have found that the objects of the present invention can be attained by using an acid-decomposable resin having a specific lactone structure. The present invention has been accomplished based on this finding.
Furthermore, as a result of extensive studies on the constituent material of a resist composition in the positive chemical amplification system, the present inventors have found that the objects of the present invention can be attained by using the above-described specific acid-decomposable resin and additionally a specific additive. The present invention has been accomplished based on this finding.
More specifically, the objects of the present invention can be attained by the following constructions.
(1) A positive photoresist composition comprising (A) a compound capable of generating an acid upon irradiation with actinic rays or radiation and (B) a resin capable of decomposing under the action of an acid to increase the solubility in alkali, containing a repeating unit having a group represented by the following formula (I): 
wherein R1 represents hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, which may have a substituent, R2 to R7, which may be the same or different, each represents hydrogen atom, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent or an alkenyl group which may have a substituent, provided that at least one of R6 and R7 is a group exclusive of hydrogen atom and R6 and R7 may combine to form a ring, and m and n each independently represents 0 or 1, provided that m and n are not 0 at the same time.
(2) The positive photoresist composition as described in (1) above, wherein the resin (B) further contains a repeating unit having an alkali-soluble group protected by at least one group containing an alicyclic hydrocarbon structure represented by the following formula (pI), (pII), (pIII), (pIV), (pV) or (pVI): 
wherein R11 represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a sec-butyl group; Z represents an atomic group necessary for forming an alicyclic hydrocarbon group together with the carbon atom; R12 to R14 each independently represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R12 to R14 or either one of R15 and R16 represents an alicyclic hydrocarbon group; R17 to R21 each independently represents hydrogen atom, a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R17 to R21 represents an alicyclic hydrocarbon group and either one of R19 and R21 represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms; and R22 to R25 each independently represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R22 to R25 represents an alicyclic hydrocarbon group.
(3) A positive photoresist composition as described in (2) above, wherein the alicyclic hydrocarbon structure-containing group represented by formula (pI), (pII), (pIII), (pIV), (pV) or (pVI) is a group represented by formula (II): 
wherein R28 represents an alkyl group which may have a substituent, R29 to R31, which may be the same or different, each represents a hydroxy group, a halogen atom, a carboxy group, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkoxy group which may have a substituent, an alkoxycarbonyl group which may have a substituent or an acyl group which may have a substituent, and p, q and r each independently represents 0 or an integer of 1 to 3.
(4) The positive photoresist composition as described in any one of (1) to (3) above, wherein the resin (B) contains a repeating unit represented by the following formula (a): 
wherein R represents hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having from 1 to 4 carbon atoms, and R32 to R34, which may be the same or different, each represents hydrogen atom or a hydroxyl group, provided that at least one of R32 to R34 represents a hydroxyl group.
(5) The positive photoresist composition as described in any one of (1) to (4) above, which further contains an acid diffusion inhibitor.
(6) The positive photoresist composition as described in any one of (1) to (5) above, wherein the compound (A) is a sulfonium salt compound of sulfonium or iodonium.
(7) The positive photoresist composition as described in any one of (1) to (5) above, wherein the compound (A) is a sulfonate compound of N-hydroxyimide or a disulfonyldiazomethane compound.
(8) The positive photoresist composition as described in any one of (1) to (7) above, wherein the exposure light used is a far ultraviolet ray at a wavelength of 150 to 220 nm.
(9) A positive photoresist composition for far ultraviolet exposure, comprising:
(A) a compound capable of generating an acid upon irradiation with actinic rays or radiation,
(B) a resin capable of decomposing under the action of an acid to increase the solubility in alkali, containing a repeating unit having a group represented by the following formula (I), and
(C) a fluorine-containing and/or silicon-containing surfactant: 
wherein R1 represents hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, which may have a substituent, R2 to R7, which may be the same or different, each represents hydrogen atom, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent or an alkenyl group which may have a substituent, provided that at least one of R6 and R7 is a group exclusive of hydrogen atom and R6 and R7 may combine to form a ring, and m and n each independently represents 0 or 1, provided that m and n are not 0 at the same time.
(10) The positive photoresist composition for far ultraviolet exposure as described in (9) above, wherein the resin (B) further contains a repeating unit having an alkali-soluble group protected by at least one group containing an alicyclic hydrocarbon structure represented by the following formula (pI), (pII), (pIII), (pIV), (pV) or (pVI): 
wherein R11 represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a sec-butyl group; Z represents an atomic group necessary for forming an alicyclic hydrocarbon group together with the carbon atom; R12 to R16 each independently represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R12 to R14 or either one of R15 and R16 represents an alicyclic hydrocarbon group; R17 to R21 each independently represents hydrogen atom, a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R17 to R21 represents an alicyclic hydrocarbon group and either one of R19 and R21 represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms; and R22 to R25 each independently represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R22 to R25 represents an alicyclic hydrocarbon group.
(11) The positive photoresist composition for far ultraviolet exposure as described in (10) above, wherein the group containing an alicyclic hydrocarbon structure represented by the following formula (pI), (pII), (pIII), (pIV), (pV) or (pVI) is a group represented by the following formula (II): 
wherein R28 represents an alkyl group which may have a substituent, R29 to R31, which may be the same or different, each represents a hydroxy group, a halogen atom, a carboxy group, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkoxy group which may have a substituent, an alkoxycarbonyl group which may have a substituent or an acyl group which may have a substituent, and p, q and r each independently represents 0 or an integer of 1 to 3.
(12) The positive photoresist composition for far ultraviolet exposure as described in any one of (9) to (11) above, wherein the resin (B) contains a repeating unit represented by the following formula (a): 
wherein R represents hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having from 1 to 4 carbon atoms, and R32 to R34, which may be the same or different, each represents hydrogen atom or a hydroxyl group, provided that at least one of R32 to R34 represents a hydroxyl group.
(13) The positive photoresist composition for far ultraviolet exposure as described in any one of (9) to (12) above, which further contains an acid diffusion inhibitor.
(14) The positive photoresist composition for far ultraviolet exposure as described in any one of (9) to (12) above, wherein the acid diffusion inhibitor is a nitrogen-containing basic compound and the nitrogen-containing basic compound is at least one compound selected from the group consisting of 1,5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene, 1,4-diazabicyclo[2.2.2]octane, 4-dimethylaminopyridine, hexamethylene-tetramine, 4,4-dimethylimidazoline, pyrroles, pyrazoles, imidazoles, pyridazines, pyrimidines, tertiary morpholines and hindered amines having a hindered piperidine skeleton.
(15) The positive photoresist composition for far ultraviolet exposure as described in any one of (9) to (14) above, wherein the compound (A) is a sulfonic acid salt compound of sulfonium or iodonium.
(16) The positive photoresist composition for far ultraviolet exposure as described in any one of (9) to (14) above, wherein the compound (A) is a sulfonate compound of N-hydroxyimide or a disulfonyldiazomethane compound.
(17) The positive photoresist composition for far ultraviolet exposure as described in any one of (9) to (16) above, wherein the exposure light used is a far ultraviolet ray at a wavelength of 150 to 220 nm.
(18) A positive photoresist composition for far ultraviolet exposure, comprising:
(A) a compound capable of generating an acid upon irradiation with actinic rays or radiation,
(B) a resin capable of decomposing under the action of an acid to increase the solubility in alkali, containing a repeating unit having a group represented by the following formula (I), and
(D) a solvent containing the following solvent (a) in an amount of 60 to 90 wt % based on the entire solvent:
(a) at least one first solvent selected from propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether propionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate and ethyl 3-ethoxypropionate. 
xe2x80x83wherein R1 represents hydrogen atom or an alkyl group having from 1 to 9 carbon atoms, which may have a substituent, R2 to R7, which may be the same or different, each represents hydrogen atom, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent or an alkenyl group which may have a substituent, provided that at least one of R6 and R7 is a group exclusive of hydrogen atom and R6 and R7 may combine to form a ring, and m and n each independently represents 0 or 1, provided that m and n are not 0 at the same time.
(19) The positive photoresist composition for far ultraviolet exposure as described in (18) above, wherein the resin (B) further contains a repeating unit having an alkali-soluble group protected by at least one group containing an alicyclic hydrocarbon structure represented by the following formula (pI), (pII), (pIII), (pIV), (pV) or (pVI): 
wherein R11 represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a sec-butyl group; Z represents an atomic group necessary for forming an alicyclic hydrocarbon group together with the carbon atom; R12 to R16 each independently represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R12 to R14 or either one of R15 and R16 represents an alicyclic hydrocarbon group; R17 to R21 each independently represents hydrogen atom, a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R17 to R21 represents an alicyclic hydrocarbon group and either one of R19 and R21 represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms; and R22 to R25 each independently represents a linear or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group having from 1 to 4 carbon atoms, provided that at least one of R22 to R25 represents an alicyclic hydrocarbon group.
(20) The positive photoresist composition for far ultraviolet exposure as described in (19) above, wherein the group containing an alicyclic hydrocarbon structure represented by the following formula (pI), (pII), (pIII), (pIV), (pV) or (pVI) is a group represented by the following formula (II): 
wherein R28 represents an alkyl group which may have a substituent, R29 to R31, which may be the same or different, each represents a hydroxy group, a halogen atom, a carboxy group, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkoxy group which may have a substituent, an alkoxycarbonyl group which may have a substituent or an acyl group which may have a substituent, and p, q and r each independently represents 0 or an integer of 1 to 3.
(21) The positive photoresist composition for far ultraviolet exposure as described in any one of (18) to (20) above, wherein the resin (B) contains a repeating unit represented by the following formula (a): 
wherein R represents hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having from 1 to 4 carbon atoms, and R32 to R34, which may be the same or different, each represents hydrogen atom or a hydroxyl group, provided that at least one of R32 to R34 represents a hydroxyl group.
(22) The positive photoresist composition for far ultraviolet exposure as described in any one of (18) to (21) above, which further contains an acid diffusion inhibitor.
(23) The positive photoresist composition for far ultraviolet exposure as described in any one of (18) to (22) above, wherein the compound (A) is a sulfonic acid salt compound of sulfonium or iodonium.
(24) The positive photoresist composition for far ultraviolet exposure as described in any one of (18) to (22) above, wherein the compound (A) is a sulfonate compound of N-hydroxyimide or a disulfonyldiazomethane compound.
(25) The positive photoresist composition for far ultraviolet exposure as described in any one of (18) to (24) above, wherein the exposure light used is a far ultraviolet ray at a wavelength of 150 to 220 nm.